Recent studies and research have been aimed at identifying new configurations of spoked wheels for bicycles leading to better performances of the wheel, as well as creating an original and innovative aesthetic effect.
Technically speaking, research in the field of spoked wheels for road racing bicycles has been directed to identifying solutions that on the one hand reduce weight, which is increasingly desirable in road racing, and on the other hand increase the static and dynamic stability of the wheel. Structural strength, particularly as it results in a reduction in the risks of failure of the spokes of the wheel, is also desired.
In road racing wheels especially, the spokes make a substantial contribution to achievement of the desired results. In fact, the spokes contribute to maintaining static and dynamic stability of the wheel. Furthermore, in rear wheels, the spokes are responsible for performing the important function of transmitting the driving torque from the wheel hub to the rim of the wheel. The driving torque transmission should occur with the maximum possible efficiency, and with minimum deformations, so as to not dissipate the energy exerted on the pedals by a cyclist. Finally, the desired results should be achieved with the minimum weight possible and without introducing risk factors for failure of the wheel spokes. From this standpoint, a particularly critical factor is the tensioning of the spokes during wheel assembly. One of the purposes of said tensioning is to guarantee that the rim will always remain “centered” or “true”, i.e., it will not shift away from a median plane of the wheel orthogonal to the axis of the hub and equidistant from the ends of the hub itself. Thus, the spokes of a typical spoked wheel include a first set of spokes on one side of the wheel, connected to a first hub portion, and a second set of spokes on the other side of the wheel, connected to a second hub portion, set at an axial distance from the first portion. Consequently, the spokes on the two sides of the wheel have an inclination or camber angle with respect to the median plane of the wheel. This inclination causes the spoke tensioning to give rise to components of force in the direction parallel to the axis of the wheel. Balancing in the components of force keeps the rim in the centered or true condition. Spoke tensioning is most critical in wheels where the spokes on the two sides of the wheel present different camber angles. This is typically the case for spokes of the rear wheel, where the wheel hub carries a sprocket cassette, where spokes set on that side have a considerably smaller inclination angle than the inclination angle of the spokes on the other side. Obviously, the spokes with smaller inclination angles must be tensioned more than the spokes on the other side in order to guarantee the centered position of the rim. Said higher tensioning gives rise to a greater risk of failure of the individual spoke. The problem of a different camber angle of the spokes on the two sides of the wheel exists not only for rear wheels. This problem exists in any wheel where that hub is partially utilized, for example, by the disk of a disk brake.
In order to solve the above mentioned problems, the applicant has already proposed and developed (see European patent application No. EP-A-1 201 458) a spoked wheel for a bicycle. The present invention sets forth another solution to the aforementioned problem.